A 62-year old male patient presents to his G.P. with a non-productive cough and hoarseness that has been ongoing for the last month. During the consultation the patient describes how he has had little appetite and has been feeling tired despite a reduction in his workload as a builder. He also discusses how he has been trying to cut down on his smoking from around 30 to 10 cigarettes per day as he has been feeling short of breath. Following a physical examination, the G.P. orders blood tests, sputum tests, and a chest X-ray. Further investigations, by CT scan and bronchoscopy, reveal a sizable mass within the left bronchus (the right lung was unremarkable).
Immunohistochemical markers CK5/6, CK7, TTF-1 and p63, are frequently used to confirm a diagnosis of adenocarcinoma of the lung. Explain the role of these markers in terms of differential expression, specificity and overall contribution to diagnosis.